"You could see a scenario where that kind of negotiation could occur over the recess and lead to a pretty big bipartisan deal," that person said. "The question would be: Who has the political motivation and/or the legislative drive and momentum to carry that off?"

Others doubt that an RES or any other controversial energy or climate package can pass the Senate this year.

"It's a pretty tough political environment right now to do something big and controversial," Sen. Lindsey Graham (R-S.C.) said Wednesday.

Graham co-authored an economywide cap-and-trade bill earlier this year with Sens. John Kerry (D-Mass.) and Joe Lieberman (I-Conn.), but dropped out of the negotiations in April two days before a planned press conference to unveil the measure.

"Until November comes and goes, from a political perspective, it's both highly unlikely that anything can happen in the early fall given the tight timeframe of the congressional calendar," or during a lame-duck session when lawmakers will lack interest, said Eric Ueland, who served as chief of staff to former Senate Majority Leader Bill Frist (R-Tenn.).

Holding out hope for a carbon cap

Despite the odds, some lawmakers and environmentalists are still optimistic that the Senate can eke out a bill that caps carbon emissions this fall.

"I think there's a chance to get some sort of a cap. I also think there's a chance to get some really meaningful clean energy provisions," said Nathan Willcox, Environment America's federal global warming program director.

Willcox said additional votes for a bill to limit emissions could emerge if the utility industry offers its support to legislation that caps just that sector.

Kerry and Lieberman, who have drafted a bill to cap emissions from just the utility sector, have said they might be able to strike a deal with the industry if given more time.

"Harry Reid, today, has committed to giving us that opportunity, that open door, if you will, over the next days, weeks, months, whatever it takes, to find those 60 votes," Kerry said yesterday. "So the work will continue every single day."

And despite an impasse between environmental groups and utilities on how to craft such a bill, it appears as though some progress was made.

According to a July 19 draft memo (pdf) obtained by The Hill, a "working group" of utility chiefs and environmentalists have reached agreement on the schedule, distribution of emissions allowances, cost controls and offsets.

Short-term scramble

Despite their decision to drastically scale back their summer energy agenda, Senate Democrats will still have plenty of work to do to pass their small energy package in the two weeks they have before August recess.

Reid said yesterday that he was confident that he would have the 60 votes to pass the bill, but Republicans have previously expressed concerns about several of the provisions, meaning bipartisan support is not necessarily a foregone conclusion.

"To be clear, we are not putting forth this bill in place of a comprehensive bill," Reid said. "But we will not pass up the opportunity to hold BP accountable, lessen our dependence on oil, create good-paying American jobs and protect the environment."

Further clouding the outlook for the package is a tight Senate schedule. Democrats want to vote on the Supreme Court nomination of Elana Kagan before recess, and they still hope to pass a small-business jobs bill.

Of the four provisions Reid has said he will include in the bill, at least three have drawn GOP fire in the past. While none appear destined to be a deal-breaker, the concerns -- and Reid's expected decision to limit amendments -- could easily cause a series of procedural hurdles that would eat up some, if not all, of the remaining summer floor schedule.

At the least, Republican leadership appears to have plenty of incentive to attempt to deny Democrats an easy legislative victory ahead of the looming November elections.

The oil spill response legislation that is expected to headline the package is likely to prove the most heavily contested.

Ueland said that if Reid's bill is too aggressive for Republicans, "he faces the challenge of dealing with the potential consequences of that."